A little desert shrub is bringing hope to the growing number of people who are allergic to rubber -- that's rubber condoms, rubber gloves, rubber boots.
Guayule (wy-oo-lee), a plant indigenous to the southwestern United States and northern Mexico, produces a hypoallergenic latex which is proving to be a substitute for hevea latex -- the offending raw material of Malaysian rubber trees that makes its way into about 40,000 different products.
Preliminary research suggests that one per cent of the general population is sensitive to hevea latex. Among health-care workers -- many of whom wear gloves eight hours a day -- that number rises to about 12 per cent.
Allergic reactions to rubber worn on the skin range from minor irritations to life-threatening anaphylactic shock. In 1988, a Toronto operating-room nurse who regularly passed out when she donned latex gloves became the first documented latex-allergic case in North America. Since then, hevea has been responsible for at least 16 deaths, lawsuits in the United States and hundreds of workers' compensation claims in Canada (more than 400 in Ontario alone). At present the only alternative is polyurethane vinyl, which is considered a poor barrier against infection.
Against that shadow, guayule offers a promising alternative. Unlike latex from the hevea brasiliensis tree of Malaysia, it will not trigger a deadly reaction, says Dr. Katrina Cornish, plant physiologist with the U.S. Department of Agriculture in Albany, California.
"We've tested now about 500 Type-I latex sensitive people who have not cross-reacted," she says.
The difference between hevea latex and guayule latex lies in their proteins. Out of hevea's 250 proteins, nine have been named and singled out as allergens, says Dr. Don Beezhold, a senior scientist at the Guthrie Research Institute in Pennsylvania.
The major allergen is probably a protein called hevein that acts like an anti-bacterial and anti-fungal agent in response to wounds -- something that happens every time a rubber tree is tapped. To make matters worse, the response intensifies with each cut. Higher demand caused by the HIV scare of the early 1980s led to more frequent tapping and to less washing away of proteins in the manufacturing process. In contrast, Guayule has 10 to 30 times fewer proteins than hevea latex processed even before that time. And guayule proteins are easily removed.
"The beauty with guayule, because the plant is a homogenate, you have to grind the plant up and start with a yucky greeny-brown colour," Dr. Cornish says. "If washed or purified improperly, you end up with yucky greeny-brown gloves."
While Dr. Cornish raves about her new gloves, to her knowledge no one has yet tried the guayule condoms. Like gloves made of guayule, the prototypes are proving more supple and resilient. With a shelf life of five years, gone may be the days when an old condom turns to dust along with armorous intentions.
And they may be available as soon as next year. Yulex Corp. of California holds exclusive rights to produce and manufacture guayule latex products.
"We would like to come into the Canadian market in unison [with the U.S.] or shortly after," says Jeff Martin of Yulex, which plans to expand production to 40,500 hectares of guayule. About 100,000 additional shrubs have been planted and first harvest is expected in 18 months. Until then, supplies are limited to 100 hectares of mature guayule growing in Arizona.
The manufacturing process invented by Dr. Cornish creates a "guayule milkshake." Branches are clipped from the shrub and put through a wet-grinding process. Latex is lighter than water and separates out when run through a centrifuge, after which it is purified.
Guayule's future looks so bright that new plantations have also been seeded in South Africa, Brazil, Mexico and Argentina. A decade ago, Agriculture Canada tried a few test plots in Delhi and Simcoe for Ontario growers seeking alternatives to tobacco, but after one year the guayule failed, confirming what they already knew -- the climate's too cold.
Too bad, because according to industry estimates, about 25 million pairs of latex surgical gloves and 100 million pairs of examination gloves made of both latex and polyurethane vinyl are sold in Canada annually. Vinyl is a poor barrier compared with latex which is considered the best protection.
Guayule will enter the market at the high end of the price range, says Mr. Martin, with costs dropping to competitive prices in a couple of years as production increase. That's good news for latex-allergic lovers, too. Right now, they pay twice the price for a safe night of polyurethane passion.